Reclosable fasteners for plastics bags and the like

ABSTRACT

A reclosable fastener or zipper comprises interengageable male and female profile members ( 12, 16 ), each provided on a base ( 13, 17 ). One or both vases is/are provided with a lateral flange ( 18, 20, 22, 24 ). One or more of such flanges is/are provided with a pair of spaced, shallow convexities ( 28 ) with a layer of sealant material ( 30 ) co-extruded into the zone or zones between the convexities.

FIELD OF THE INVENTION

[0001] This invention relates to a closure strip or zipper for use as a reclosable fastener for plastics bags, pouches, etc. It is also concerned with methods of manufacturing such fasteners. Such zippers comprise male and female profile elements located on a pair of opposed base members. The base members are arranged to be bonded to a substrate, such as a film, in the manufacture of the reclosable bags, pouches, etc. Each base member and its profiled element are co-extruded. Such a zipper is usually flanged, i.e. with one or both of the base members extending laterally out beyond the region of the male/female closure.

[0002] It is known to provide zippers where an adhesive is provided on the flange or flanges, to aid in the welding of the flange or flanges to a substrate, i.e. a plastics film or web.

[0003] One of the ongoing objectives in the design of such zippers is to reduce the heat required to seal the flanges to the substrate material. Excessive heat is always a problem and the lower the sealing temperature the easier it is to produce an acceptable product.

[0004] Another objective is to avoid or at least minimise leakage of the adhesive material.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to seek to meet both these objectives.

[0006] In accordance with the invention there is provided a reclosable fastener comprising interengageable male and female profile members, each provided on a base, and with one base being connected to a lateral flange, wherein said flange is provided with a pair of spaced, shallow convexities with a layer of sealant material co-extruded into the zone between the convexities.

[0007] Also in accordance with the invention there is provided a reclosable fastener comprising interengageable male and female profile members, each provided on a base, and with at least two lateral flanges connected to one base or to the two bases, wherein one or more of said flanges is provided with a pair of spaced, shallow convexities with a layer of sealant co-extruded into the zone or zones between the convexities.

[0008] Also in accordance with the invention there is provided a method of extruding a reclosable fastener which comprises extruding a male profile member on a base and a female profile member on a base, with a lateral flange connected to one base and with a pair of spaced, shallow convexities proud of the flange, and co-extruding a layer of sealant material into the zone between the convexities.

[0009] Also in accordance with the invention there is provided a method of extruding a reclosable fastener which comprises extruding a male profile member on a base and a female profile member on a base, with at least two lateral flanges connected to one base or to the two bases, and with a pair of spaced, shallow convexities on one or more of said flanges, and co-extruding a layer of sealant material into the zone or zones between the convexities.

[0010] Preferably, in the co-extrusion process, the sealant material does not fill the zone or zones right up to the zone ends. When pressure is applied in the sealing of the zipper to the film or web, there is therefore space into which the sealant material can travel, thereby reducing the risk of leakage.

[0011] In a multi-flanged zipper this zone of infilled sealant material can be provided on some or all the flanges.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order that the invention may be more fully understood, an embodiment of zipper in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which:

[0013]FIG. 1 is a shadowgraph of the zipper in accordance with the invention; and,

[0014]FIG. 2 is a schematic illustration giving typical dimensions for a flange of the zipper shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] Referring first to FIG. 1, this shows a zipper comprising a first profile member 10 having a male element 12 on a base 13 and a second profile member 14 having a female element 16 on a base 17. The profile members 10, 14 can be extruded polymeric material, such as LDPE. The first profile member 10 has two lateral flanges 18 and 20 extending from the base 13. The second profile member 14 has two lateral flanges 22 and 24. The second profile member 14 is connected to its flanges 22, 24 not centrally but at a margin of the base 17, thereby to provide a hinged link via a leg, 26.

[0016] Each of the flanges 18, 20, 22, 24 is provided with a pair of spaced, shallow convexities 28 formed from the material of the flange. Between the respective pairs of convexities 28 are infilled, co-extruded layers 30 of a sealant material, such as EVA for example. In the co-extrusion process, the sealant material preferably does not wholly fill the zones between the convexities 28, but stops short of the zone ends and is slightly proud of the convexities. In this way, when heat and pressure is applied in the process of sealing the flanges to an adjoining substrate, the sealant material will be squeezed into the space left available, reducing in thickness to the depth of the convexities. Thus, leakage of sealant will be reduced or eliminated.

[0017]FIG. 2 shows flange 18 on an enlarged scale and schematically. The dimensions given in FIG. 2 are in millimetres. It will be noted that the convexities 28 are not both the same length; the one nearer the profile of the zipper is longer. However, they could be of the same length. Also, the thickness of the outer end 32 of the flange is less than the thickness of the inner portion 34 of the flange. Again, these thicknesses could be the same, depending upon the extrusion process. The thickness of the sealant layer is 0.070 mm. This is about 44% of the overall thickness of the flange 18 at this zone.

[0018] The dimensions are summarised as follows: Length of sealant layer 3.000 mm Thickness of sealant layer 0.070 mm Thickness of convexities 0.070 mm Length of outer end 32 of flange 0.500 mm Thickness of outer end 32 of flange 0.110 mm Thickness of inner end 34 of flange 0.160 mm

[0019] These dimensions are given by way of example only.

[0020] Although in the illustrated embodiment the reclosable fastener or zipper is shown as having four flanges, the invention is equally applicable to a zipper having one, two or three flanges. In the case of a multi-flanged zipper, one or more of the two, three or four flanges may be provided with the two shallow, sealant-constraining convexities. 

1. A reclosable fastener comprising interengageable male and female profile members, each provided on a base, and with one base being connected to a lateral flange, wherein said flange is provided with a pair of spaced, shallow convexities with a layer of sealant material co-extruded into the zone between the convexities.
 2. A reclosable fastener comprising interengageable male and female profile members, each provided on a base, and with at least two lateral flanges connected to one base or to the two bases, wherein one or more of said flanges is provided with a pair of spaced, shallow convexities with a layer of sealant co-extruded into the zone or zones between the convexities.
 3. A reclosable fastener according to claim 2, in which each base is connected to two respective lateral flanges.
 4. A reclosable fastener according to any preceding claim, in which the layer of sealant material is of the order of 3 mm in lateral width.
 5. A reclosable fastener according to any preceding claim, in which the layer of sealant material is of the order of 0.07 mm in thickness.
 6. A reclosable fastener according to any preceding claim, in which the thickness of the layer of sealant material is of the order of 44% of the combined thickness of the sealant and flange.
 7. A reclosable fastener according to any preceding claim, in which the convexity which is nearer to the profile member has a greater lateral width than the convexity which is further from the profile member.
 8. A reclosable fastener according to any preceding claim, in which the thickness of the flange or flanges is less outwardly of the outer convexity than inwardly of the inner convexity.
 9. A reclosable fastener according to any preceding claim, in which one said base is connected by a hinge joint to a lateral flange or flanges.
 10. A method of extruding a reclosable fastener which comprises extruding a male profile member on a base and a female profile member on a base, with a lateral flange connected to one base and with a pair of, spaced, shallow convexities proud of the flange, and co-extruding a layer of sealant material into the zone between the convexities.
 11. A method of extruding a reclosable fastener which comprises extruding a male profile member on a base and a female profile member on a,base, with at least two lateral flanges connected to one base or to the two bases, and with a pair of spaced, shallow convexities on one or more of said flanges, and co-extruding a layer of sealant material into the zone or zones between the convexities.
 12. A method according to claim 10 or 11, in which in the said co-extrusion process the sealant material does not fill the zone or zones to the zone ends. 